The present invention relates generally to a laser control circuit in a recordable optical disc player, and more particularly to the circuit for controlling laser output of variable high level and low level.
The recordable optical disc may be formed of various composition materials at the record surface thereof and have various recording sensitivities depending on the composition materials. When making records on such an optical disc, the optimum laser output of the high level therefor is also varied depending on the composition materials. The optical disc player, thus, should be adapted so as to generate the optimum laser output at the high level depending on the optical disc to be used, and consequently the laser output of the high level should be adapted to be controllable for that purpose.
On the other hand, the optical disc player must be capable of generating the predetermined level output, during generation of the low level output, so as to make the tracking and focussing controls possible during the recording operation. It is desired, thus, to provide a laser control circuit whereby the high level output may be controlled while keeping the low level output constant.
Additionally, in order to stabilize the laser output, in view of the fact that laser element properties are varied depending on ambient conditions such as temperature, there has been used in general a negative feedback loop in the laser output circuit. This negative feedback circuit, however, may sometimes adversely affect laser output control.